Virtually all of the present knowledge on intestinal blood flow regulation has been obtained from whole organ preparations in which the behavior of large populations of microvessels is integrated within a flow response. Adenosine, prostaglandins, and oxygen have been implicated in certain forms of regulation, but, in general, their roles are uncertain, which may reflect a combination of insensitive techniques and interactions within the regulatory system. To probe the behavior of the individual microcirculatory elements, the relative contributions, and interactions between, these three substances in glucose-induced absorptive hyperemia will be investigated in a superfused hamster intestinal preparation. Blood flow, tissue PO2, and capillary density changes will be measured with intravital microscopic techniques. The vasoactivity of adenosine during the hyperemia will be estimated indirectly by making paired comparisons between a vehicular control group and between a group treated to block adenosine receptors and increase the rate of adenosine deamination. Prostaglandins (E and I) released into a superfusate during absorption will be measured with radioimmunoassay and the vasoactivity will be estimated by comparing the responses of a control group to those of a group with synthesis blocked. The information potentially derived from this work will further define the basic mechanism involved in regional blood flow control.